Coating structure and method for forming the same

Abstract

A coating structure for a metal member includes a surface-smoothing layer formed on the metal member for smoothing a surface of the metal member, and a fluorine-based film formed on the surface-smoothing layer. The fluorine-based film can be formed by applying a fluorine-containing solution on the surface-smoothing layer, and by drying the fluorine-containing solution. The coating structure can be suitably used for a fuel injection nozzle.

1 . A coating structure for a metal member comprising:
 a surface-smoothing layer, formed on the metal member, for smoothing a surface of the metal member; and   a fluorine-based film formed on the surface-smoothing layer.   
     
     
         2 . The coating structure according to  claim 1 , wherein:
 the surface-smoothing layer includes a NiP/PTFE composite film in which PTFE particles are dispersed in NiP.   
     
     
         3 . The coating structure according to  claim 2 , wherein:
 the NiP/PTFE composite film is formed by an electroless plating.   
     
     
         4 . The coating structure according to  claim 2 , wherein:
 a content rate of the PTFE particles in the NiP/PTFE composite film is about 7 to 9 wt %.   
     
     
         5 . The coating structure according to  claim 2 , wherein:
 a particle size of the PTFE particles is about 0.2 to 1 μm.   
     
     
         6 . The coating structure according to  claim 2 , wherein:
 a thickness of the NiP/PTFE composite film is about 5 to 20 μm.   
     
     
         7 . The coating structure according to  claim 2 , wherein:
 the surface-smoothing layer further includes a Ni strike film which is formed on the metal member, as an adhesion layer; and   the NiP/PTFE composite film is formed on the Ni strike film.   
     
     
         8 . The coating structure according to  claim 7 , wherein:
 a thickness of the Ni strike film is about 0.5 to 1.5 μm.   
     
     
         9 . The coating structure according to  claim 7 , wherein:
 the surface-smoothing layer further includes a NiP film which is formed on the Ni strike film, as a ground layer;   and the NiP/PTFE composite film is formed on the NiP film.   
     
     
         10 . The coating structure according to  claim 2 , wherein:
 the surface-smoothing layer further includes a NiP film formed on the metal member, as a ground layer; and   the NiP/PTFE composite film is formed on the NiP film.   
     
     
         11 . The coating structure according to  claim 10 , wherein:
 a thickness of the NiP film is about 0.5 to 1.5 μm.   
     
     
         12 . The coating structure according to  claim 2 , wherein:
 a surface roughness of a surface, on which the NiP/PTFE composite film is formed, is not more than about 5 μm.   
     
     
         13 . The coating structure according to  claim 2 , wherein:
 a surface roughness of the NiP/PTFE composite film is not more than about 0.1 μm.   
     
     
         14 . The coating structure according to  claim 1 , wherein:
 the surface-smoothing layer includes a diamond-like carbon film.   
     
     
         15 . The coating structure according to  claim 14 , wherein:
 the diamond-like carbon film is formed by a method selected from a plasma CVD, a sputtering, and an ion plating.   
     
     
         16 . The coating structure according to  claim 14 , wherein:
 a thickness of the diamond-like carbon film is about 0.5 to 5 μm.   
     
     
         17 . The coating structure according to  claim 14 , wherein:
 a surface roughness of a surface, on which the diamond-like carbon film is formed, is not more than about 10 μm.   
     
     
         18 . The coating structure according to  claim 14 , wherein:
 a surface roughness of the diamond-like carbon film is not more than about 10 μm.   
     
     
         19 . The coating structure according to  claim 1 , wherein:
 the fluorine-based film includes a fluoroalkylsilane.   
     
     
         20 . The coating structure according to  claim 1 , wherein:
 a thickness of the fluorine-based film is about 0.01 to 0.5 μm.   
     
     
         21 . The coating structure according to  claim 1 , wherein:
 the metal member is a Fe-based member.   
     
     
         22 . A method for forming a coating structure, comprising:
 forming a surface-smoothing layer on a metal member to smooth a surface of the metal member;   applying a fluorine-containing solution on the surface-smoothing layer; and   drying the fluorine-containing solution to form a fluorine-based film.   
     
     
         23 . The method for forming a coating structure according to  claim 22 , wherein:
 the forming of the surface-smoothing layer includes
 applying a NiP/PTFE-containing solution, in which PTFE particles are dispersed in NiP, to the metal member, and 
 drying the NiP/PTFE-containing solution to form a NiP/PTFE composite film. 
   
     
     
         24 . The method for forming a coating structure according to  claim 23 , wherein:
 the NiP/PTFE composite film is formed by an electroless plating.   
     
     
         25 . The method for forming a coating structure according to  claim 23 , wherein:
 a content rate of the PTFE particles in the NiP/PTFE composite film is about 7 to 9 wt %.   
     
     
         26 . The method for forming a coating structure according to  claim 23 , wherein:
 a particle size of the PTFE particles is about 0.2 to 1 μm.   
     
     
         27 . The method for forming a coating structure according to  claim 23 , wherein:
 a thickness of the NiP/PTFE composite film is about 5 to 20 μm.   
     
     
         28 . The method for forming a coating structure according to  claim 23 , wherein:
 the forming of the surface-smoothing layer further includes applying a Ni-containing solution on the metal member to form a Ni strike film as an adhesion layer, before forming the NiP/PTFE composite film.   
     
     
         29 . The method for forming a coating structure according to  claim 28 , wherein:
 a thickness of the Ni strike film is about 0.5 to 1.5 μm.   
     
     
         30 . The method for forming a coating structure according to  claim 28 , wherein:
 the forming of the surface-smoothing layer further includes applying a NiP-containing solution on the Ni strike film to form a NiP film as a ground layer, before forming the NiP/PTFE composite film.   
     
     
         31 . The method for forming a coating structure according to  claim 23 , wherein:
 the forming of the surface-smoothing layer further includes applying a NiP-containing solution on the metal member to form a NiP film as a ground layer, before forming the NiP/PTFE composite film.   
     
     
         32 . The method for forming a coating structure according to  claim 31 , wherein:
 a thickness of the NiP film is about 0.5 to 1.5 μm.   
     
     
         33 . The method for forming a coating structure according to  claim 23 , wherein:
 a surface roughness of a surface, on which the NiP/PTFE composite film is formed, is not more than about 5 μm.   
     
     
         34 . The method for forming a coating structure according to  claim 23 , wherein:
 a surface roughness of the NiP/PTFE composite film is not more than about 0.1 μm.   
     
     
         35 . The method for forming a coating structure according to  claim 22 , wherein:
 the surface-smoothing layer includes a diamond-like carbon film.   
     
     
         36 . The method for forming a coating structure according to  claim 35 , wherein:
 the diamond-like carbon film is formed by a method selected from a plasma CVD, a sputtering, and an ion plating.   
     
     
         37 . The method for forming a coating structure according to  claim 35 , wherein:
 a thickness of the diamond-like carbon film is about 0.5 to 5 μm.   
     
     
         38 . The method for forming a coating structure according to  claim 35 , wherein:
 a surface roughness of a surface, on which the diamond-like carbon film is formed, is not more than about 10 μm.   
     
     
         39 . The method for forming a coating structure according to  claim 35 , wherein:
 a surface roughness of the diamond-like carbon film is not more than about 10 μm.   
     
     
         40 . The method for forming a coating structure according to  claim 22 , wherein:
 the fluorine-based film includes a fluoroalkylsilane.   
     
     
         41 . The method for forming a coating structure according to  claim 22 , wherein:
 a thickness of the fluorine-based film is about 0.01 to 0.5 μm.   
     
     
         42 . The method for forming a coating structure according to  claim 22 , wherein:
 the metal member is a Fe-based member.   
     
     
         43 . A fuel injection nozzle comprising:
 a nozzle body having a guide hole; and   a needle inserted in the guide hole of the nozzle body; wherein:   the coating structure according to  claim 1  is formed on a part of the needle as the metal member.   
     
     
         44 . The fuel injection nozzle according to  claim 43 , wherein:
 the nozzle body further includes
 a sliding hole part adjacent to an axial opening end of the guide hole, 
 a fuel storing part provided in the guide hole, 
 a valve seat provided at a leading end of the guide hole, and 
 a plurality of injection holes provided to penetrate though the valve seat; and 
   the needle includes
 a sliding part inserted in the sliding hole part to be slidable, 
 a valve part for opening and closing the injection holes by seating on or separating from the valve seat such that when the valve part of the needle is separated from the valve seat of the nozzle body, fuel which is supplied between the nozzle body and the needle is injected from the injection holes, and 
 a shaft part for connecting the sliding part and the valve part. 
   
     
     
         45 . The fuel injection nozzle according to  claim 44 , wherein:
 the surface-smoothing layer is formed on the shaft part and a part of the sliding part.   
     
     
         46 . The fuel injection nozzle according to  claim 44 , wherein:
 the surface-smoothing layer is formed on the valve part, the shaft part, and a part of the sliding part.   
     
     
         47 . The fuel injection nozzle according to  claim 44 , wherein:
 the fluorine-based film is formed on a part of the shaft part.   
     
     
         48 . The fuel injection nozzle according to  claim 44 , wherein:
 the fluorine-based film is formed on the valve part and a part of the shaft part.   
     
     
         49 . The fuel injection nozzle according to  claim 47 , wherein:
 the fluorine-based film is formed on an area which is not less than about 80% of the shaft part.